长江中下游地区汛期暴雨频次的时空分布特征

利用长江中下游地区六省一市1960~2003年81个台站汛期（5~9月）逐日降水资料，统计出了不同台站近44年逐年汛期暴雨事件的发生频次，并进行了时空分布特征分析。结果表明：汛期暴雨事件最频发的区域在皖南到赣北一带，而北部的鄂北和皖北是最少发的区域；一致性异常特征是长江中下游地区汛期暴雨事件发生频次的最主要空间模态；汛期暴雨事件发生频次可分为以下5个主要的空间分型：两湖平原型、北方型、长江沿江型、南方型、沿海型；从长期变化趋势来看，两湖平原型、长江沿江型和沿海型暴雨事件发生频次表现为较明显的增加趋势，南方型基本没有长期变化趋势，但有先降后升的特点，而北方型表现为弱的减少趋势；近44年来暴雨事件发生频次各分区的周期振荡不太一致。

SPATIAL AND TEMPORAL FREQUENCY DISTRIBUTION IN TORRENTIAL RAIN EVENTS IN FLOOD SEASON IN MIDDLE AND LOWER REACHES OF YANGTZE RIVER

By using the daily precipitation data of 81 stations in six provinces and one city in the middle and lower reaches of Yangtze River during the 1960~2003 flood season (from May to September), the annual torrential rain event genesis frequency in different stations were obtained by statistical method, and its spatial and temporal distribution in last 44 years were studied. Southern Anhui Province and Northern Jiangxi Province are the areas where the genesis frequency is the highest, while Northern Hubei and Northern Anhui the lowest. Over the middle and lower reaches of Yangtze River, the consistent abnormal characteristics is the main spatial distribution pattern. There are five main spatial distribution types: two lakes and plain type (Ⅰ), northern type (Ⅱ), Yangtze River type (Ⅲ), southern type (Ⅳ) and coastland type (Ⅴ). From the long term change, types Ⅰ, Ⅲ and Ⅴ showed obvious increasing trend. Although the observation was not in a long-term, type IV showed decreasing trend first and then increasing trend. Type II had a slight decreasing trend. The oscillation period of these distributions are un consistent over the last 44 years.